The slowness of page load mentioned by folks here is the reason why I think caching at the HTTP level (ex: Varnish) is much more efficient than caching at the service level (ex: Memcached), which is much further down the stack and is bound to be latency-sensitive. Because it's much less entangled in your code and deep into your infrastructure (less technical debt). A hybrid approach can work too but only if it's light and unobtrusive.

By the way, and I'm going out on a limb with my shameful plug, I built a Varnish-as-a-Service kind of infrastructure called Cachoid ( https://www.cachoid.com ). But to my own defense, I'm putting my energy, time, and money where my mouth is.